Shunt for speaking-telephone systems



. F. W. JONES. V Shunt for Speaking Telephone Systems;

No. 238,912. J Patented March 15,1881.

"$55015. PMOTO-LITHOGRAPHER, WASNINETON, D C.

signaling electro-magnetsincluded in the main UNITED STATES PATENTOFFICE.

FRANCIS W. JONES, OF CHICAGO, ILLINOIS.

SHUNT FOR SPEAKING-TELEPHONE SYSTEMS.

SPECIFICATION forming part of Letters Patent No. 238,912, dated March15, 1881.

Application filed August 25, 1879.

To all whom it may concern:

Be it known that I, FRANCIS W. JONES, a citizen of the United States,residing in Chicago, in the county of Cook and State of Illinois, haveinvented anew and useful Improvement in Circuits for Telephone-Lines, ofwhich the following is a specification.

My invention relates more particularly to that class of telephone-linesin which the alarm or signaling apparatus is operated by voltaiccurrents or by magneto-electric pulsations. In

operating this class of telephone-lines it is frequently desirable andnecessary to place several difi'erent stations upon the same circuit,and also, as a matter of economy and convenience, to make use of thesame conductor, both for signaling and for conversation, by means ofsuitable speaking-telephones of well-known construction. A practicaldifliculty has, however, been found to exist by reason of thisorganization of apparatus and circuits. The signaling apparatus at eachstation being actuated by an electro-magnet of theordinaryconstruct-ion, it is obvious that this electro-magnetmustremain at alltimes in the main circuit, except when the telephone "at the samestation is in use, so that signals may be received on it at any moment;but it has been found by experience that telephonic vibrations orundulations are checked by being caused to pass through anelectro-magnet, or, as it is sometimes expressed, an electro magnet ismore or less opaque to rhythmical vibrations. Consequently, if a numberof stations are placed upon the same line, with their several circuit,the telephonic vibrations which are transmitted to and fro between anytwo stations communicating with each other must necessarily pass throughall the electro-magnets in the circuit except their own, and by thismeans the vibrations are weakened or absorbed to such an extent as torender conversation nearly or quite inaudible.

The object of my invention is to obviate this difficulty by furnishin ga path for the telephonic vibrations to pass the stationwithoutnecessaril'y going through the coils of the electromagnet, Whileat the same time the said electro magnet is so arranged as to respond ofone polarity.

line.

In the accompanying drawings, Figure 1 is a diagram illustrating theapplication of my improvements to a signaling electro-magnet actuated byvoltaic or other electric currents Fig. 2 represents the application ofthe same to a signaling apparatus operated by alternating positive andnegative pulsations, such as are produced by a magnetoelectricgenerator.

Referring to the drawings, It represents an ordinary electro-magnet,which is supposed to be placed at a station upon the telephone-line.This electro-magnet is provided with the usual soft-iron armature andpivoted lever T, which latter may be utilized to actuate the signalingapparatus in any suitable or well-known manner. For example, it maybearranged as a relay to repeat the signals by means of a local batteryupon a sounder, a bell, or other like instrument, or a bell-hammer maybeattached directly to the lever T, as shown in Fig. 2. The armatureleverT may be provided with the ordinary retracting-spring, as shown in thedrawing. The armature-leverT vibrates between two contaet-stops, 3 and 5A shunt or branch circuit is connected with the main line at the point2, and goes first to the point of the armature'lever at the point I,through said lever and its rear contact-stop, 3, and thence by a wire tothe point 4 on the main line beyond the electro-magnet R. The lastnamedcircuit, from the point2 to the point 4, constitutes a shunt-circuitpassing around the electro-magnet R. In the position of the apparatusrepresented in Fig. 1 the current of the main line has been cut off atsome other station, in order to leave the line clear for the operationof the telephone. Consequently, the electro-magnet R has becomedemagnetized, and the armature-lever T, being released, is held againstthe contact-stop 3, thus closing the shunt-circuit around theelectro-magnet. Unless the resistance of the helix of the electro-magnetIt is very small it is necessary to insert an artificial resistance orrheostat, S, at some point in the shunt-circuitas, for instance, betweenthe points 1 and 2, as shown readily to signaling-eun'ents traversingthe in the drawing. In most cases the resistance mo of this shunt shouldbe at least equal to that of the helix of the electro-magnet R forgiving signals or alarms, although this proportion may be widelydeparted from without rendering the apparatus inoperative.

If the rhcostat is composed of a coil of wire it should be wound withhalf its convolutions in the reverse direction to the other half, inorder to neutralize the effects of self-induction.

The operation of the apparatus is as follows: When the parts are in theposition shown in Fi 1, it a signaling-current is sent through the lineit will divide at the point 2, one portion going through the, coils ofthe electromagnet R to the pointa, and the other portion going throughthe shunt, by the way of l and 3, to the same point 4, thus passingaround or avoiding the electro-magnet. The electromagnet being thuscaused to attract its armature, the first movement of the latterinterrupts the contact between the lever T and the stop 3 and breaks theshunt-circuit, after which the power of the entire current passesthrough the coils of the eleetro-magnet, and a signal is produced by theaction ofits armature 'l in the manner hereinbefore described. If,however, a series of rhythmical or telephonic vibrations traverses thesame line these will be too weak to afiect the armature of theelectro-magnet R, which will at the same time tend to obstruct theirpassage, as before explained; but another available route is open tothem by way of the shunt-circuit, which, in this case, remains unbroken,as the rhythmical vibrations are not powerful enough to cause thearmature of the electro-magnet to be attracted, so as to break contactat the stop 3. It is obvious, therefore, that these rhythmical ortelephonic vibrations may be transmitted past any required number ofstations, and that they will, for the most part, pass around theelectro-magnets by way of the several shunt-circuits, and that theiramplitude will be preserved with little or no diminution.

Fig. 2 shows the application of my invention to a double-actingelect-ro-magnet having a polarized armature vibrating between fixedcontact-stops. In this apparatus, when there is no current upon the mainline the armature-lever will remain at rest against the front or therear contact-point indiiierently, its position depending solely upon thepolarity of the current last traversing the line, whether positive ornegative. In this case the only modification necessary in applying myinvention thereto is to connect the point at of the main line to boththe front and rear contactstops, 3 and 3, as shown in the drawin 1 donot broadly claim herein the application of a shunt to anelectro-inagnct for the purpose of conveying telephonic vibrationsaround said magnet, in combination with a a rheostat having its coilswound in opposite directions to neutralize self-induction therein, asthese features form the subject-matter of another division ofthisapplication. Neither do I claim herein the combination of anelectro-magnet, armature, armature-lever, and contactstops with a mainline, a circuit-connection between both the front and back contact-stopsand the main line ata point on one side of the electro-magnet, and acircuit-connection between the arinature-lever and the main line at apoint on the opposite side of the electro-magnet, because I propose toembrace it in a subseuent application.

I claim as my invention- The combination, substantially as hereinbeforeset forth, of an electro-magnet, armature, armature-lever, andcontact-stops with amain line in which said electro-inagnet is included,a circuit-connection between the back contact-stop and a point in themain line on one side of the electro-magnet, a circuit-connectionbetween the armature-lever anda point on the opposite side of theelectro-magnet, and an artificial resistance included in one of saidcircuit-connections.

FRANCIS W. JONES.

Witnesses:

ANSON S. TEMPLE, A. O. THOMAS.

